This relates generally to dealing with congestion in a cellular link between a video source and a video sink where the video source sends video data and the video sink receives the video data.
This relates generally to dealing with congestion in a wireless link between a wireless video device which transmits video data to a wireless base station, where the wireless video device can be decomposed in a video source (Open System Interconnection (OSI) Model layer 7) and a network sink (OSI Model layers 3-2-1) including a modem which transmits video data over a cellular link to the wireless base station.
Congestion may occur in the wireless link unbeknownst to the video sender. This is because the congestion happens in layers 1 and 2 and the information about the congestion may be held at layer 2 (which corresponds to the modem layer that transmits the video data). However, the video source in OSI Model layer 7, or the application layer, which decides what data to send, may be oblivious to the congestion. As a result, the video source can continue to push data from layer 7 to layer 2 but the modem is unable to effectively transmit because of the congestion.
Current cellular specifications for video calls have a bitrate adaptation mechanism. The mechanism attempts to cause the video sender to control its video bitrate based on feedback which the video receiver reports to the sender using a Temporary Maximum Media Stream Bitrate Request (TMMBR) Real-Time Transport Protocol (RTCP) message or by using packet loss statistics from receiver reports. However, the TMMBR does not always achieve successful bitrate adaptation because it may not be supported by devices, may not always be reliable, may be lost, and is not particularly well suited for use in the uplink path. And packet loss based estimation may not be as accurate or as timely as other estimation techniques.